Method for separating cobalt from oxo-reaction products



Jan. 17, 1967 TosHlHlDE Goro ETAL 3,298,779

METHOD FOR SEPARATING COBALT FROM OXO-REACTION PRODUCTS Filed June 19, 1,962

INVENTOR;

United States Patent O 3,298,779 METHOD FOR SEPARATING CBALT FROM @XG-REACTION PRODUCTS Toshihide Goto, Nishinomiya-shi, and Akio Yamagishi and Takao Sawada, Niihama-shi, Japan, assignors to Sumitomo Chemical Company, Ltd., Osaka, Japan, a corporation of Japan Filed .lune 19, 1962, Ser. No. 203,630

Claims priority, application Japan, June 23, 1961, 36/22,486; July 12, 1961, 3dS/25,017 Claims. (Cl. 23-117) This invention relates to a method for separating cobalt from oxo-reaction products, and to an apparatus used for the same.

The method wherein an organic compound having an olenic double bond is contacted with carbon monoxide and hydrogen at an elevated temperature and at an elevated pressure in the presence o-f a cobalt-containing catalyst to produce an aldehyde of one more carbon number than the starting organic compound or derivatives of the aldehyde, has been well known as so-called oxoprocess and has been worked commercially. In such oxoreaction products just after the reaction, the cobalt-containing catalyst employed remains dissolved mainly in the form of cobalt carbonyl, cobalt hydrocarbonyl, and otherv unknown carbonyl complex salts in which the cobalt is combined with carbon monoxide, along with a minor amount of organic acid salts of cobalt. These carbonyl compounds often cause a number of difliculties, for example, they cause deterioration of the oxo-reaction produ-ct, particularly of the aldehyde product, in the subsequent steps, such as distillation or hydrogenation of the product. Also, they give rise to a partial blockade by isolation and deposition of metallic cobalt at various portions of the apparatus, thereby an obstacle to the continuous operation being caused. Moreover, the cobalt catalyst is expensive. For these reasons, the cobalt catalyst in the product is ordinarily separate-d and recovere-d from the product prior to the subsequent processes.

Various methods have been known for the separation and recovery of cobalt from the oxo-reaction products. These conventional methods involve, when broadly classied, (l) the one in which metallic cobalt is isolated by heat-decomposition of the catalyst through contact with steam, and then separated by ltration, magnetic attraction, or other suitable means, (2) the one in which metallic cobalt is isolated by heat-decomposition of the catalyst in the presence of hydrogen at a superatmospheric pressure and then separated by filtration, magnetic attraction, or other suitable means, and (3) the one in which a cobalt salt insoluble in the oxo-reaction product and soluble in water is formed by contact of the catalyst with an acid and then filtered off, or extracted with water.

However, the method (l) has various difliculties that the metallic cobalt formed is in nely divided form which makes its separation difficult, that the isolation of metallic cobalt is not uniform, for instance, metallic cobalt is isolated and deposited mainly around the opening for supply of the oxo-reaction product to the heating zone or around the steam-blowing nozzle, and causes partial blockade, and that metallic cobalt once formed needs troublesome procedures to reuse for the oxo-catalyst. The method (2) involves similar problems to those of method (l).

As to the method (3), although it is advantageous in that the cobalt is recovered in the form of aqueous solution and is easily handled, some difficulties are encountered, for example, conversion velocity of the cobalt catalyst to the cobalt salt is comparatively lower and varies even under a determined condition. Therefore, a considerably I large scale of apparatus for contact-extraction is needed,

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and a -denite extraction time is unexpectable, so that the operation is difficulty controllable.

As the result of the researches on separating of cobalt from oxo-reaction product, the present inventors have discovered a method for separating cobalt efliciently, by improving such conventional methods in which the oxoreaction product is treated with an acid, thereby obviating the shortcomings in the old methods.

An object of the invention is to provide a method for separating and recovering cobalt dissolved in oxoreaction product in a high and controllable conversion velocity. Another object is to provide a method for separating and recovering such cobalt with a more economical operation than those previously employed. Still another object is to provide an apparatus used for such method, by which apparatus the separation of cobalt is effected rapidly with moderate conditions. Other objects willbe apparent from the following description.

Accordingly, the invention provides a method for separating cobalt from oxo-reaction product, which comprises contacting an oxo-reaction product containing a cobalt catalyst with an aqueous inorganic acid solution in the presence of oxydizing agent, particularly air.

The oxo-reaction product contains cobalt value in a dissolved state in an amount corresponding to the cobalt catalyst used. In general, the amount of cobalt value dissolved ranges from 0.1 to 5 g./l. When the oxo-reaction product containing cobalt dissolved thereinis contacted with an aqueous inorganic acid solution having a concentration of l to 10% by weight in the presence of an oxydizin-g agent, preferably an oxygen-containing gas,

particularly air, at room temperature or somewhat higher, the cobalt is converted to an inorganic salt within a period of time from several minutes to l hour, depending upon the states of agitation rand contact, and substantially completely transferred to the aqueous layer. The aqueousy layer containing inorganic salt of cobalt is separated from the oily layer comprising the oxo-reaction product. The oily layer accompanies `a small amount of the aqueous cobalt salt solution in emulsied state, but the amount of cobalt in the oily layer is generally less than 10 mg./l., and such a small amount of cobalt salt does not affect the subsequent steps. If desired, of course, the oily layer is washed with water or centrifuged to remove the contaminated cobalt salt. The inorganic salt of cobalt separated as an aqueous solution can 'be converted to an organic salt of cobalt by addition of a caustic alkali and an organic acid such as naphthenic acid, and extracted with an olen material for oxo-reaction or a solvent, to be reused as catalyst for oxo-reaction.

The inorganic acid used in the method of the present invention is preferably selected from strong inorganic acids, for example, sulfuric acid, hydrochloric acid, phosphoric acid, etc., among which sulfuric acid is the most preferable. The inonganic acid is used in the form of an aqueous solution which has a concentration of 1 to 10% by weight, more preferably about 5%. When a continuous method is contemplated, an oxo-reaction product and an aqeuous inorganic acid solution are continuously fed to a contacting zone, while the contacted mixture is continuously withdrawn from the zone and allowed to stand to be separated in two layers. In this case, it is preferable to recycle the separated aqueous layer, containing the dissolved cobalt salt Iand excess of the inorganic acid, -to said contacting zone. The amount of the aqueous inorganic acid solution required varies depending upon the concentration, i.e. the lower concentration needs the larger amount and vice versa. In general, the amount employed is Iwithin the range between 0.01

uct.

As the oxydizing agent fused in the method of the present invention, an oxygen-containing gas, particularly air or oxygen-enriched air, is the most economical from the industrial points of view, although an agent having stronger oxydizing power, such as hydrogen peroxide may be used if desired. When an oxygen-containing gas is used, it is most effective when supplied to the contacting zone by blowing into the mixture of oxo-reaction production and aqueous inorganic acid sol-ution, but it is suicient to be merely passed over the surface of the mixture when a powerful agit-ation is employed or when a horizontal type of agitation as described below is employed.

In carrying out the method of the invention, the conversion time is shortened by keeping efiicient contact of the oily layer consisting of oxo-reaction product with the aqueous layer consisting of aqeuous inorganic acid solution. It is an advantage of the invention that the time for the separation of cobalt is rather shorter, as compared with the conventional cases. I'For example, even in the case of eifecting the reaction by use of a broadly employed vessel equipped with a vertical type agitator under an ordinary agitating condition, cobalt is substantially completely transferred to the aqueous layer within about l hour. If a much more powerful agitation is employed, a much shorter time is secured. Degree of agitation depends upon peripheral velocity of end of stirring blades, and recommended velocity is about 60,000 min/min. For example, when stirring blades having 200 mm. diameter in a `vessel of 320 mm. diameter is rotated at a rate of 300 rpm., the time required is shortened up to 10 minutes or less.

The features of the present invention are further displayed by use of a horizontal type apparatus having a horizontally rotating agitator, by lwhich an eicient re- -moval of cobalt is effected with an ordinary rotating condition within a shorter time.

The present inventors have devised a novel type of such apparatus, which comprises a horizontally placed vessel of cylindrical configuration; a rotating shaft passing through in the vessel with the same axial direction to that of the vessel; a plurality of pairs of stirring blades which are mounted along said shaft; three inlet means for introduction of an oxo-reaction product, an aqueous inorganic acid solution and an oxygen-containing gas, respectively, and two outlet means for withdrawal of the resulting liquid mixture and the exhaust gas, respectively, attached at the other end of the vessel, the outlet for the liquid mixture being located at a level approximately same to that of the highest position of the end of the rotating blades, and the outlet for the gas being located at a level higher than that of the outlet for the liquid mixture. In more preferable and advantageous modifications, the shaft may be provided with an axis level lower than that of the vessel. The plurality of pairs of stirring blades may be mounted with differential phases. The diameter of pair of stirring blades is preferably two third or more of the diameter of the vessel. If desired, a number of bafe plates may be mounted between each adjacent pair of the blades, on the shaft or on the inner surface of the vessel.

FIGURES 1 and 2 of the attached drawings show one example of such suitable horizontal type apparatus to contact oxo-reaction product with an aqueous inorganic acid solution in the presence of oxygen-containing gas according to the present invention.

FIGUR-E l is a diagrammatical side view of the apparatus, and FIGURE 2 is a section view of the apparatus at A-A in FIGURE 1. In FIGURE l, an oxo-reaction product, an aqueous inorganic acid solution and an oxygen-containing gas are introduced into the contacting zone 7 through inlet means l, 2 and 3. In the contacting zone 7, which is a vessel of cylindrical coniiguration, there is provided a shaft which is rotated at a rate of 30 to 200 r.p.m. A plurality of pairs of stirring blades 6 are mounted along the shaft with differential phases.

The diameter of a pair of stirring blades is two third of the diameter of the vessel. A number of bale plates 8 are mounted on the shaft between each adjacent pair of the blades. The oxo-reaction product and `the aqueous inorganic acid solution are well agitated in the presence yof the oxygen-containing gas by means of the stirring blades. After a retention time of about 10 minutes or more in the contacting zone 7, the resulting liquid mixture is withdrawn from the liquid outlet means 4, while the exhaust gas is discharged from the gas outlet means 5. A liquid retention time of at longest 30 minutes suces :to transfer the cobalt dissolved in the oxoreaction production to the aqueous phase in a cobalt salt form. The liquid mixture withdrawn through the outlet means 4 is introduced into a settling vessel which is not shown and separated into two layers. The upper layer is an oxo-reaction product containing only 10 mg./l. or less of cobalt. The liquid surface in the contacting zone 7 is preferably so adjusted that it is at a level not so higher than the'highest position of the end of the rotating blades 6 or it is rather at a little lower level. Number of the pairs of blades does not so much aifect to the effectiveness of thecontact.

In the present invention, use of an inorganic acid is essential for dissolution of cobalt to an aqueous layer. If an organic acid is employed, instead, a sufficiently large conversion velocity from cobalt to its salt is not obtained. Besides, a considerable amount of the organic acid per se and its cobalt salt remains dissolved in oxo-reaction product.

According to the method of the invention, cobalt dissolved in oxo-reaction product can be easily and rapidly removed up to a level lower than 10 mg./l. This method is extremely advantageous, since the inorganic acid and oxygen-containing gas, if it is used, are exceedingly inexpensive, therefore the method is economical. Also, such benets as saving of power cost and easy administration of apparatus are obtained when an apparatus as described above is used, because efficient and rapid separation of cobalt from oxo-reaction product is secured with an ordinary agitating condition. As an accompanying effect of the invention, a short time is required for the separation possibilities use of a smaller scale apparatus, with economical advantage.

Now, the method of the invention will be further described with reference to the examples, which are, however, set forth only for the Ipurpose of illustration and not for the purpose of limitation.

EXAMPLE l One liter of an oxo-reaction product obtained by a reaction of iso-heptene, carbon monoxide and hydrogen in the presence of a cobalt catalyst and containing 1800 ing/l. of cobalt in dissolved state, is mixed with 400 cc. of sulfuric acid of 5% by weight concentration. The resulting mixture is stirred for 1 hour at ordinary temperature, while air is blown thereinto. After that time, the mixture is allowed to separate into two layers, and the lower layer, i.e. the aqueous layer containing cobalt in the form of sulfate, is removed. The upper, oily layer is washed with a small amount of water. This experiment is repeated thrice. The amount of cobalt remaining dissolved in the oily layer after each procedure is 10.2, 7, and 4.2 mg./l., respectively. These values show that the oily layer after any stage of procedures is an oxoreaction product containing little amount of cobalt, which can be used for the subsequent process without difficulty.

EXAMPLE 2 In a vertically cylindrical vessel, 22 liters of the oxoreaction product, which is same as used in Example l, and 5 liters of sulfuric acid of 2% by weight concentration, are charged. While passing air through the space above the surface of the liquid mixture at the rate of 2000 l./hr., a stirrer of 200 mm. diameter, equipped in the vessel of 320 mm. diameter, is rotated at 500 r.p.m. for 10 minutes. After allowing the liquid mixture to separate into two layers, the upper layer is decanted. This experiment is repeated twice. The amount of cobalt remaining dissolved in the oily layer after each procedure is 6.3 and 8.7 mg./l., respectively.

EXAMPLE 3 Into a horizontal type contacting apparatus having length of 0.5 rn. and diameter of 200 mm., as shown iu FIGURE 1, an oxo-reaction product containing 1500 Ing/l. of dissolved cobalt and sulfuric lacid of 5% by weight concentration are continuously introduced at the rates of 30 l./hr. and l 1./hr., respectively. Air is forced to pass through the inlet into the upper space portion at the rate of 1500 l./hr. The stirring blades are rotated at comparatively low rate of 120 r.p.m., thereby the both liquid layers being well contacted with each other in the presence of air. The liquid mixture is withdrawn from the liquid outlet pipe in a velocity corresponding to the charging velocity. The oily layer, i.e. oxo-reaction product, obtained after separation from the aqueous layer, contains only 3 mg./l. of cobalt dissolved. This means that 99.8% of cobalt originally dissolved was removed.

What We claim is:

1. A method for separating cobalt from oxo-reaction .products produced by reaction of an organic compound having an oleinic double bond, carbon monoxide and hydrogen in the presence of a cobalt-containing catalyst at an elevated temperature and at an elevated pressure, which comprises contacting said oxo-reaction product with an aqueous sulfuric acid solution in the presence of an oxidizing agent selected from the group consisting of air and hydrogen peroxide to form phases consisting of an aqueous phase and an organic phase and to transfer the cobalt compound involved in said oxo-reaction product to said aqueous phase in the form of cobalt sulfate.

2. A method according to the claim 1, wherein said aqueous sulfuric acid solution has a concentration of l to 10% by weight.

3. A method according to the claim 1, wherein said oxidizing agent is hydrogen peroxide.

4. A method according to the claim 1, wherein said oxidizing agent is air.

5. A method according to claim 1, wherein the liquid mixture obtained after the contact of the oxo-reaction product with the aqueous sulfuric acid -solution is allowed to separate into two layers, and the aqueous layer containing excess of sulfuric acid is reused as the aqueous sulfuric acid solution to be used for the contact.

References Cited by the Examiner UNITED STATES PATENTS 2,526,707 10/1950 Stahl et al. 23-117 2,647,819 8/1953 McGauley 23-117 2,758,915 8/1956 Vodonik 23-285 3,014,970 12/1961 Johnson et al 260-604 X 3,063,815 1l/1962 Redniss 23-285 3,196,171 7/1965 Gunter et al. 23-117 X O OSCAR R. VERTIZ, Primary Examiner.

MAURICE A. BRINDISI, Examiner.

E. C. THOMAS, Assistant Examiner. 

1. A METHOD FOR SEPARATING COBALT FROM OXO-REACTION PRODUCTS PRODUCED BY REACTION OF AN ORGANIC COMPOUND HAVING AN OLEFINIC DOUBLE BOND, CARBON MONOXIDE AND HYDROGEN IN THE PRESENCE OF A COBALT-CONTAINING CATALYST AT AN ELEVATED TEMPERATURE AND AT AN ELEVATED PRESSURE, WHICH COMPRISES CONTACTING SAID OXO-REACTION PRODUCT WITH AN AQUEOUS SULFURIC ACID SOLUTION IN THE PRESENCE OF AN OXIDIZING AGENT SELECTED FROM THE GROUP CONSISTING OF AIR AND HYDROGEN PEROXIDE TO FORM PHASES CONSISTING OF AN AQUEOUS PHASE AND AN ORGANIC PHASE AND TO TRANSFER THE COBALT COMPOUND INVOLVED IN SAID OXO-REACTION PRODUCT TO SAID AQUEOUS PHASE IN THE FORM OF COBALT SULFATE. 